Impostor syndrome

Another that also works is realizing that all the rest are also just fumbling along. Everybody is not perfect. And you may be pretty good at faking it by now. :)

I find that never making mistakes isn't the skill to strive for; being able to notice a mistake and recover from it is a lot more useful. It takes a lot of practice (at making mistakes, and fixing them) to develop it, too.

Confidence, for me, doesn't come from never getting anything wrong. Because I will be distracted or working from a wrong hypothesis, and it will be a mess. It comes from believing (from sufficient experience) that I can fix it if it goes pear-shaped.